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Subject: Re: sleep timer
From: BlueChip (cs_bluechip_at_webtribe.net)
Date: 2004-06-14


>>I use the sleep timer a hell of a lot and wanted to ask this
>>question: Does the timer switch off the box straight away or does it
>>first ensure the drive has finished spinning so as to avoid that
>>horrible/'scary noise the HDD makes when it instantly loses power?
>
> From a quick glimpse in the code, it looks like it doesn't check if the
> disk is spinning before it shuts down.
>
>>I ask this as i'm slightly worried about damaging my brand new Box
>>this way...perhaps the problems with my original one were caused by
>>this?
>
>Not sure. Some people claim that it doesn't damage the drive, some say it
>does.
>
>Linus

Should the head touch the surface of one of the disk platters, you will
experience a "head crash" ...small pieces of the platter surface material
will be 'scratched' off and thrown about inside the hdd unit.

The gap between the platter and the head is about 1/10th the thickness of a
human hair. Should some particulate matter enter that gap, you get a
further "head crash".

So once the head has hit the platter once, the damage curve is exponential.

It it the air disturbance caused by the spinning platters that keep the
head from touching the surface.

If you remove the power while the head is over the middle (or worse still
extreme) of a platter, the hdd unit has to snap the heads back before it
runs out of eletricity and the platters stop spinning.

Of course with modern technology the risk has been minimised, I remember a
day when you wouldn't dare think of moving a spinning hard drive
...nowdays, I think it fun to play gyroscope games with them. I have a
friend who thinks it's clever to hot-swap IDE drives.

But if you want to do things properly, shut the drive down before ripping
the power out of it.

If you want to do things anally, you should not only be shutting down the
hdd, but also the adac and probably some other stuff as well. This would
require an OFF feature in Rockbox.

BlueCHip

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